High Performance Lubricating Compositions

ABSTRACT

An oleaginous corrosion-resistant lubricating composition comprising at least one poly-alpha olefin synthetic oil and effective amounts of metal salts of sulfonic acids metal salts of carboxylic acids, metal salts of mixtures or combinations of sulfonic and carboxylic acids, alkylated aromatic compounds as solubility modifiers, pour-point depressants, at least one antioxidant, and metal deactivator compounds.

CROSS-REFERENCE to RELATED APPLICATIONS

This Application is a Continuation-In-Part of U.S. patent application Ser. No. 14/591,118 filed Jan. 7, 2015.

STATEMENT OF GOVERNMENT INTEREST

The Invention described herein may be manufactured and used by or for the Government of the United States of America for government purposes without the payment of any royalties thereon or therefore.

FIELD OF THE INVENTION

This invention relates to lubricating compositions and methods of using lubricating oils compositions that can be applied by spraying/brushing onto metal parts for long-term protection to minimize environmental effects particularly on aircraft parts. High performance, long lasting, preservative lubricating oils has been developed for use in internal airframe applications in the military fleet to reduce the cost of corrosion maintenance and to improve the fleet's readiness. This invention is focused on optimizing a blend of oils, corrosion inhibitors, antiwear agents, antioxidants, and other additives to form high-performance lubricating oils. Lubricating oils generally comprise a majority of base oil and a variety of chemical additives to impart improved properties. The novel lubricating oil of this invention is intended for lubrication and protecting against corrosion of aircraft parts, certain small arms, automatic weapons and whenever a general purpose, water-displacing, low-temperature lubricating oil is required. Lubricants are typically used to separate moving parts systems. This lubricating oil has the benefit of reducing friction and surface fatigue, together with reduced heat generation, operating noise, and vibrations of moving parts. Currently, several formulations have been developed and tested on the requirements of MIL-PRF-32033 specification and corrosion prevention properties. Based on these testing results, the new oil formulations have shown superior performance compared to the existing MIL-PRF-32033 oil products.

BACKGROUND OF THE INVENTION

Corrosion is a costly factor in the Department of Defense. Aircraft and other weapon systems are old, and structural damage from corrosion is a life-limiting factor on some of these aircraft. One of the factors contributing to corrosion is that existing preservative lubricating oils have not proven to be effective for more than a few days or weeks and therefore require repeated applications. The MIL-PRF-32033 specification is currently used by DoD services as a preservative lubrication oil to maintain aircraft. MIL-PRF-32033 is a general purpose, water displacing, lubricating oil with preservative properties, and is intended for the lubrication and preservation of aircraft components. It is used mainly as a general-purpose lubricant in all applications where water displacement, water resistance, corrosion protection and/or low temperature performance is required.

The NAVAIR Corrosion Fleet Focus Team has indicated that the corrosion protection of the current lubricating oils is not sufficient and require repeated applications. The goal of this invention was to develop high performance general-purpose lubricating oil products, per MIL-PRF-32033, to reduce the maintenance cost and meet the fleet needs. This invention will benefit the Naval Aviation Enterprise (NAE) by providing a more efficient, cost effective and high performance lubricating oil for aerospace applications. The cost savings will be realized through reduced maintenance costs and enhanced mission readiness.

SUMMARY OF THE INVENTION

More specifically, this invention relates to oleaginous or lubricating oil compositions consisting essentially of one or more poly-alpha olefin synthetic lubricating oils having a viscosity requirement that meets the specification of MIL-PRF-32033. The synthetic lubricating oil comprises effective amounts of metal salts consisting of sulfonic acids, carboxylic acids, and combinations of said metal salts, pour-point depressants comprising hydrotreated distillate heavy-paraffinic additives, one or more antioxidants such as the aromatic amines, metal deactivation, and alkylated aromatic compounds.

It is an objective of this invention to provide oleaginous compositions to protect against corrosion or rust of small arms, automatic weapons, aircraft parts and the like.

It is another objective of this invention to provide liquid oleaginous compositions resistant to corrosion.

It is a further objective of this invention to provide an oleaginous composition and a method of using the composition to form a rust-resistant coating on metal surfaces.

These and other objectives of the invention will become apparent by reference to the detailed description.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to oleaginous corrosion-resistant compositions and to the method of inhibiting corrosion or rust on various metal compound surfaces including metals such as aluminum, aluminum alloys and various ferrous metals. The oleaginous oil compositions of this invention consist essentially of, in parts by weight, from about 70 to 85 parts and preferably from 75 to 80 parts of at least one poly-alpha olefin synthetic lubricating oil, and various mixtures of said synthetic oils, 5.0 to 15 parts and, preferably from 8.0 to 12 parts of oil soluble compounds comprising corrosion inhibitors selected from the group consisting of sulfonic acid metal compounds, carboxylic acid metal compounds, and oil soluble compounds derived from the reaction of sulfonic acids and carboxylic acids with a metal compound with about 5.0 to 15 parts and preferably from 12 to 15 parts of an oil soluble alkylated aromatic compound as a solubility modifier, from about 0.1 to 1.0 part and preferably 0.3 to 0.5 parts of an oil soluble pour-point depressant, such as hydrotreated distillate heavy-paraffinic additives, from about 0.1 to 2.0 or 1.0 to 1.5 parts of at least one antioxidant, such as an aromatic amine e.g., a diphenylamine, and from about 0.1 to 0.5 or 0.1 to 0.3 parts of a metal deactivator such as a triazole compound.

For example, the preferred corrosion inhibitors are derived from the reaction of at least one sulfonic acid such a naphthalene sulfonic acid and at least one carboxylic acid such as a fatty acid with a metal or metal compound to form the metal salt or metal complex. The corrosion inhibitors are derived from the stoichiometric reaction of a metal or metal compound such as an alkaline earth metal with a naphthalene sulfonic acid and a carboxylic acid, preferably at least one or more of these acids, to form the metal salt or complex.

The sulfonates may be prepared from sulfonic acids which are typically obtained by the sulfonation of alkyl substituted aromatic hydrocarbons as those obtained by the alkylation of aromatic hydrocarbons such as by alkylating benzene, toluene, xylene, or preferably naphthalene. Specific examples of the sulfonic acids include petroleum sulfonic acids, naphthalene sulfonic acids, such as the dialkylnaphthalene sulfonic acids, wherein the alkyl group has from 1 to 12 and preferably from 7 to 10 carbon atoms, petroleum sulfonic acids, dodecylbenzene sulfonic acid, dinonylnaphthalene sulfonic acid and the like. These sulfonic acids are known in the art, and for this invention, the equivalent weight of a sulfonic acid is the molecular weight divided by the number of sulfonic acid groups.

The carboxylic acids used in preparing the carboxylic acid-metal compounds and the metal complexes include the aliphatic, cycloaliphatic, mono- and polycarboxylic acids. The aliphatic acids contain at least 6 and preferably at least 12 carbon atoms. The aliphatic carboxylic acids can be saturated or unsaturated. Specific examples of the carboxylic acids include 2-ethylhexanoic acid, linolenic acid, substituted maleic acids, linoleic acid, lauric acid, oleic acid, ricinoleic acid, palmitic acid, and mixtures of two or more carboxylic acids. The preferred carboxy acids include the fatty acids having the formulas C_(n)H_(2n-1) COOH or C_(n)H_(2n-3). The equivalent weight of these carboxylic acids is the molecular weight divided by the number of acid groups. The corrosions inhibitors can be prepared from a mixture, in any ratio, of the sulfonic acid and the carboxylic acid with a metal compound.

Preferably, the sulfonates, carboxylates and the complexes are derived from the reaction of the sulfonic acid and carboxylic acid with a metal compound such as a compound of calcium, barium, magnesium, or any other metal compound. These metal neutralizing compounds include the metal oxides, hydroxides, carbonates, bicarbonates, and mixtures thereof. These corrosion-resistant metal salts and complexes are derived from the reaction of these metal compounds with stoichiometric amounts of either one of the acids or a combination of the acids to form the metal salts of both acids or the complex thereof.

The polyvalent metal compounds and particularly the divalent metals of Group two of the Periodic Table reacted with both the sulfonic acid and carboxylic acid will result in a combination of a sulfonic acid and carboxylic acid metal salt or complex as illustrated by the following chemical structure:

The dinonylnaphthalene sulfonate/carboxylate metal complex or compounds are derived from the reaction of stoichiometric amounts of both a sulfonic acid and a carboxylic acid with a metal compound e.g., calcium hydroxide to obtain the combined metal compound or complex as illustrated. For example, in the combination, the sulfonic acid can range from 1 to 10 parts and the carboxylic acid can range from about 1 to 10 parts by weight.

The pour-point depressants are known as lube oil flow improvers that lowers the temperature at which the fluid will flow or can be poured. Typical of these compounds which improve the flow temperature or fluidity of the synthetic oil include the dialkylfumarate/vinyl acetate copolymers, polyalkylmethacrylates, esters of methacrylic acid, and the alkylated naphthalenes. Preferably, Cristol-PPD LX-150 (Hydrotreated Distillate Heavy-Paraffinic Compounds) are used as pour-point depressant additives to meet the pour-point requirements of the MIL-PRF-32033 specification. It was necessary to add the pour-point depressant compound to the formulation to improve the oil's performance at low temperatures (−40° C.). The pour-point depressant is added to the corrosion-resistant compositions in amounts ranging from about 0.1 to 1.0 parts by weight, and preferably from about 0.3 to 0.5 parts.

The following formulations are examples of the high-performance lubricating compositions.

Lubricating Oil Compositions EXAMPLE 1

Parts by weight (a) Synfluid PAO-2 cST (Boiling Point 223° C.) 70-85 (Poly-Alpha Olefin-Synthetic Fluid, Base Oil or (1-Decene, Dimer homopolymer, hydrogenated) 75-80 And/Or Synfluid PAO-4Cst (Boiling Point 414° C.) (Poly-Alpha Olefin-Synthetic Fluid, Base Oil) (1-Decene, homopolymer, hydrogenated) (b) NA-SUL CA-HT3 (Corrosion Inhibitor)  5-15 (Calcium Dinonylnaphthalenesulfonate/Carboxylate) or (Reaction of the sulfonic and carboxylic acids  8-12 with calcium compounds) (c) Cristol-PPD LX-150 0.1-1.0 (Hydrotreated distillate heavy paraffinic compound or (Pour-Point Depressant) 0.3-0.5 (d) NA-Lube K R 007A  5-15 (Alkylated Aromatic Additive) or 12-15 (e) NA-Lube AO-130 0.1-2.0 (Nonylated Diphenylamine, Antioxidant) or NA-Lube AO-242 and/or 0.1-1.5 (Butylated, octylated diphenylamine, Antioxidant) NA-Lube ADTC (and/or) (Methylene-bis-dibutyldithiocarbamate, Antioxidant) (f) K-CORP ® NF-200 0.1-0.5 (Benzotriazole and Derivatives, Metal Deactivator) or 0.1-0.3

EXAMPLE 2

The composition of Example One except the corrosion inhibitor is an alkaline earth metal salt of an alkylaryl sulfonic acid.

EXAMPLE 3

The composition of Example One except the corrosion inhibitor is an alkaline earth metal salt of an aliphatic carboxylic acid.

EXAMPLE 4

The composition of Example One except the corrosion inhibitor is derived from a stoichiometric reaction of a zinc compound with a mixture, in any ratio, of a fatty acid and a sulfonic acid.

EXAMPLE 5

The composition of Example One except the corrosion inhibitor is derived from the stoichiometric reaction of an alkaline earth metal compound with a naphthalene sulfonic acid and an aliphatic carboxylic acid to obtain the sulfonic acid-carboxylic acid metal salt complex.

The kinematic viscosity requirements of MIL-PRF-32033 specification is specified in Table 1.

TABLE 1 Kinematic viscosity, mm²/s) @ 40 degrees Celsius (° C.), minimum. 11 @ −40° C., maximum. 7,000 @ −54° C. maximum. 60,000

Neutral Salt Spray Test

The salt spray test for the oil compositions and various commercial products were performed in accordance with the ASTM B117 method. Table 2 shows the salt spray test results for the formulation compared to several commercial products qualified to MIL-PRF-32033. The new formulation of this invention showed superior performance compared to the existing MIL-PRF-32033 products. Steel panels coated with commercial products lasted only one to two days in the salt spray cabinet compared to four (4) days for steel panels coated with the new formulation. Further, aluminum panels coated with commercial products lasted less than five days in the salt spray cabinet while panels coated with the new formulation lasted more than 14 days.

TABLE 2 New Formulation FTM 5322 Corrosivity Test (240 hours) 50% relative humidity, 79° F. Pass FTM 4001.2 Salt Fog Steel  4 days Aluminum 14 days 4.2.5.5 Mil 32033 Film Characteristics Pass FTM 3458 Low Temperature Stability Pass 3.3.2.1 Mil 32033 Removability Pass

The new formulation was tested to the requirements of MIL-PRF-32033 specification and showed excellent results as shown in Table (3). The results in Table (3) indicate that the formulation meets or exceeds the requirements of MIL-PRF-32033 specification.

TABLE (3) Test Results of the Formulation to the Requirements of MIL-PRF-32033 Specification Specification New Test Method Limit Formulation Viscosity ASTM D445 @ 40 C., cSt, min 11      12.18 @−40 C., cSt, max 7,000    1509 @−54 C., cSt 60,000    9956 Pour Point, C., max ASTM D97 −57     −60 Low Temperature FTM 3458 Flow Freely Flow Freely Stability, −45 C. for 72 Hours Flash Point, C., min ASTM D92 135     178 Copper Strip Corrosion ASTM D130 2a    1a Wear Preventive, max ASTM D4171 1.0     0.43 Color of finished Fluid. ASTM D1500 7.0   2 Corrosiveness of ASTM D1748 No Corrosion No Lubricating oil to Corrosion Bimetallic Couple Oxidation Corrosion FTM 5308.6 No Corrosion No Corrosion

The intended use of the lubricating oil composition of this invention was described in Section 6.1 of the MIL-PRF-32033 specification. The lubricating oil composition is intended for lubrication and protecting against corrosion of certain small arms and automatic weapons and whenever a general purpose, water-displacing, low-temperature lubricating oil is required. Oil becomes very viscous at low temperatures so that its use at temperatures below −40° C. is limited by many machine design factors and should be proved for any specific item application by testing before adoption. The availability of this composition in gas-pressurized containers will prove to be beneficial for use in areas difficult to preserve by existing procedures. This preservative oil should not be used however, to protect fuel systems and combustion chambers of engines which are preserved in accordance with standard procedures. Composition contains carboxylic acids which could react with certain metals present in the fuel system, forming soaps which could contribute to fuel filter plugging etc.

The developed preservative lubricating oil composition aims to reduce the cost of maintaining aircraft systems, and extend the life of aircraft platforms. Application of the newly developed composition will increase fleet readiness and provide significant cost savings to the end user. Expected Department of Defense benefits include decreased aircraft downtime due to fewer scheduled maintenance inspections and maintenance actions; increased aircraft availability; and reduced corrosion repair costs, hazardous materials, and maintenance man-hours.

While the specific examples have described this invention, it is obvious to one skilled in the art that there are other variations and modifications which can be made without departing from the spirit and scope of the invention as particularly set forth in the appended claims. 

1. A corrosion-preventing free-flowing lubricating composition consisting essentially of, in parts by weight of: 70 to 85 parts of poly-alpha olefin synthetic lubricating oil, 5.0 to 15 parts of at least one oil soluble corrosion inhibitor selected from the group consisting of sulfonic acid metal compounds, carboxylic acid metal compounds and compounds derived from the stoichiometric reaction of a combination of sulfonic acids and carboxylic acids with a metal compound. 5.0 to 15 parts of an oil soluble alkylated aromatic compound, 0.1 to 1.0 parts of a pour-point consisting essentially of a heavy-paraffinic compound, 0.1 to 2.0 parts of an oil soluble antioxidant, and 0.1 to 0.5 parts of a metal deactivator compound.
 2. A corrosion-preventing free-flowing lubricating composition consisting essentially of from about, in parts by weight, 70 to 85 parts of at least one poly-alpha olefin synthetic lubricating oil, 5.0 to 15 parts of at least one sulfonic metal compound, 5.0 to 15 parts of an oil soluble alkylated aromatic compound, 0.1 to 1.0 parts of a pour-point consisting essentially of a heavy-paraffinic compound, 0.1 to 2.0 parts of an oil soluble antioxidant, and 0.1 to 0.5 parts of a metal deactivator compound.
 3. A corrosion-preventing free-flowing lubricating composition consisting essentially of from about, in parts by weight, 70 to 85 parts of at least one poly-alpha olefin synthetic lubricating oil, 5.0 to 15 parts of at least one carboxylic acid metal compound, 5.0 to 15 parts of at least an oil soluble alkylated aromatic compound, 0.1 to 1.0 parts of a pour-point consisting essentially of a heavy-paraffinic compound, 0.1 to 2.0 parts of an oil soluble antioxidant, and 0.1 to 5.0 parts of a metal deactivator compound.
 4. A corrosion-preventing free-flowing lubricating composition consisting essentially of from about, in parts by weight, 70 to 85 parts of at least one poly-alpha olefin synthetic lubricating oil, 5.0 to 15 parts of a compound derived from the stoichiometric reaction of a sulfonic acid and a carboxylic acid with a metal compound, 5.0 to 15 parts of an oil soluble alkylated aromatic compound, 0.1 to 1.0 parts of a pour-point consisting essentially of a heavy-paraffinic compound, 0.1 to 2.0 parts of an oil soluble antioxidant, and 0.1 to 0.5 parts of a metal deactivator compound.
 5. The composition of claim 1 wherein the free-flowing lubricant is a mixture of poly-alpha olefin oils having different viscosities and boiling points.
 6. The composition of claim 1 wherein the free-flowing lubricant is a mixture of poly-alpha olefin lubricating oils having kinematic viscosity of 1509 at −40° C.
 7. The composition of claim 1 wherein the pour-point depressant consists essentially of hydrated distillate heavy-paraffinic compounds.
 8. The composition of claim 1 wherein the sulfonic acid compound is an alkaline earth metal compound of a dialkylnaphthalene sulfonic acid.
 9. The composition of claim 8 wherein the dialkylnaphthalene sulfonic acid is a dialkylnaphthalene sulfonic acid metal compound wherein the alkyl group of said sulfonic acid has two to twelve carbon atoms.
 10. The composition of claim 1 wherein the pour-point is an acrylic compound.
 11. A process of preventing corrosion of metal which comprises applying an effective amount of a corrosion-preventing free-flowing lubricating composition on said metal; said composition consisting essentially of, in parts by weight, 70 to 85 parts of a poly-alpha olefin lubricating oil, 5 to 15 parts of at least one corrosion inhibitor selected from the group consisting of sulfonic acid metal compounds, carboxylic acid metal compounds and a compound derived from the stoichiometric reaction of a sulfonic acid and a carboxylic acid with a metal compound. 5.0 to 15 parts of an oil soluble alkylated-aromatic compound 0.1 to 1.0 parts of a pour-point consisting essentially of a heavy-paraffinic compound. 0.1 to 2.0 parts of an oil soluble antioxidant and 0.1 to 0.5 parts of a metal deactivator compound.
 12. The process of claim 11 wherein the poly-alpha olefin synthetic oil is a mixture of synthetic oils having different viscosities.
 13. The process of claim 11 wherein the pour-point is a hydrotreated distillate heavy paraffinic compound.
 14. The process of claim 11 wherein the corrosion inhibitor is an alkaline earth metal compound of an alkylnaphalene sulfonic acid.
 15. The process of claim 11 wherein the corrosion inhibitor is an alkaline earth carboxylic acid metal compound.
 16. The process of claim 11 wherein the pour-point is an ester of methacrylic acid.
 17. The process of claim 11 wherein the antioxidant is diphenylamine.
 18. The process of claim 11 wherein the lubricating composition has a viscosity of about 1509 at −40° C. 